Waterjet propulsion apparatus

ABSTRACT

A waterjet propulsion apparatus comprising a motor, an impeller driven by the motor via a drive shaft, and a power source. A fluid flow-path is formed through the apparatus, the flow-path extending from at least one fluid inlet, through two propulsion passages, each propulsion passage extending from a propulsion inlet to an outlet located at a rear end of the apparatus. The impeller is located within the flow-path, after the at least one fluid inlet, and before the propulsion inlet of the each of the propulsion passages. The motor is located outside of the flow-path, between the two propulsion passages, and behind the impeller. The apparatus is advantageous in that it provides a compact and lightweight construction that can, for example, be used as part of a personal marine propulsion device that can be used by an individual.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to United Kingdom Patent ApplicationNo. 1809698.2 filed on Jun. 13, 2018, the entire contents of which areincorporated by reference herein.

DESCRIPTION Field of the Invention

The present invention relates to a waterjet propulsion apparatus. Theapparatus is particularly suitable for use in a personal marinepropulsion device (sometimes known as dive propulsion vehicles) that canbe held by an individual or otherwise attached to an individual to aidtheir propulsion through and under water. Such devices are generallyused for leisure purposes but also have applications in any othersituation in which it might be desirable to propel an individual throughwater without the use of a larger vehicle.

Background

Various personal marine propulsion devices are currently known.Typically, such devices consist of a propeller driven by a motor and apower supply contained within a watertight housing. The propeller isgenerally external to the housing but contained within a casing thatallows water to be drawn through the propeller but protects the userfrom coming into contact with the propeller. The devices generally havehandles formed on an outer surface of the housing to allow a user tohold onto the device during use. When in use, a user will hold thedevice out in front of them or between their legs in order to propelthemselves through the water. These devices are relatively inefficientand provide only weak propulsion.

More recently personal marine propulsion devices using waterjet, ratherthan propeller, propulsion have become available. Waterjet propulsion isthe method of propulsion utilised in jetskis. In waterjet propulsion,water is drawn through a flow-path formed through a device by means ofan impeller located within the flow-path. Typically the flow-pathconsists of a passage having a single intake and a single outlet and theimpeller is located centrally within the passage. Steering is achievedby changing the direction in which water leaving the outlet is directedusing one or movable steering flaps or other equivalent means located inor at the outlet. The intake is generally positioned ahead of theimpeller and is, for example, positioned on the lower side of a jetski.In a typical waterjet propulsion system the motor is positioned directlyin front of the impeller outside of the flow-path and drives theimpeller by means of a drive shaft that extends into the flow-path. Inorder to allow this construction the flow-path will typically deviatebeneath or to the side the motor and the intake will be positionedbeneath or to the side of the motor.

Personal marine propulsion devices having waterjet propulsion aredesirable as the propulsion is generally more powerful and safer thanpropeller propulsion. However, the length of flow-path required toachieve efficient waterjet propulsion has been considered to makewaterjet propulsion generally unsuitable for personal marine propulsiondevices. In particular, currently available devices are excessivelylarge and/or heavy.

SUMMARY OF THE INVENTION

The present invention provides a waterjet propulsion apparatus for apropulsion device comprising a motor, an impeller driven by the motorvia a drive shaft, and a power source; wherein:

a fluid flow-path is formed through and contained within the apparatus,the flow-path extending from at least one fluid inlet located at a frontend of the apparatus through two propulsion passages, each propulsionpassage extending from a propulsion inlet to an outlet located at a rearend of the apparatus;

the impeller is located within the flow-path, after the at least onefluid inlet, and before the propulsion inlet of the each of thepropulsion passages; and

the motor is located outside of the flow-path, within a rear portion ofthe apparatus, between the two propulsion passages, and behind theimpeller.

The present invention is advantageous in that it provides a waterjetpropulsion apparatus that has a construction that allows it to be madeto be very lightweight and compact. For example, the waterjet apparatusis suitable for use in a personal marine propulsion device and wouldallow such a device to be constructed to be lightweight and compactenough for it to be used by an individual without difficulty. Thepositioning of the motor at the rear of the apparatus the two propulsionpassages results in a compact construction that can be significantlyshorter in length than waterjet propulsion devices according to theprior art. Further, the flow-path having two propulsion passages afterthe impeller, rather than a single passage, allows the flow-path afterthe impeller to be provided in a more compact manner as compared to theprior art without reducing the outlet area, whilst still providingstable and directed propulsion.

The structure of the apparatus of the present invention also ensuresthat the fluid inlets can be substantially unobstructed by any otherpart of the apparatus. In particular, there is no need for any fluidinlet to deviate around the motor and/or the drive shaft as both thedrive shaft and impeller are located behind, rather than in front of,the impeller.

The apparatus of the present invention comprises a suitable power sourcefor driving the motor. In embodiments of the invention the power sourcemay be a compact battery, such as used in similar existing apparatus.

In order to achieve a strong and directed thrust from the outlets of thepropulsion passages, each propulsion passage may progressively reduce incross-section from its propulsion inlet to its outlet. Forming thepropulsion passages in this manner is advantageous in that results in acontrolled decrease in pressure along each passage, and an increasedvelocity of the water exiting the propulsion passages, which can provideimproved thrust at the outlets of the propulsion passage.

In order to achieve well directed thrust from the outlets of thepropulsion passages said outlets may be substantially cylindrical,rectangular or any other suitable shape. If the apparatus of the presentinvention is used in a personal marine propulsion device there is norequirement for the apparatus or device to comprise means to change thedirection of the water leaving the outlets of the propulsion passages.If no such means are present then a device comprising the apparatus ofthe present invention can be steered by the user directing the deviceappropriately. However, embodiments of the invention may comprisesteering means located at or adjacent the outlets of the propulsionpassages in order to vary the direction of the water exiting the outletsand thereby steer a device comprising the apparatus. Any such steeringmeans can be formed in any manner apparent to the person skilled in theart, for example in the manner in which steering means of conventionaljetskis are formed.

The propulsion passages may be formed in any manner apparent to theperson skilled in the art. In embodiments of the invention bothpropulsion passages may be defined by a unitary splitter component thatis mounted within the housing. For example, the unitary splitter may bea moulded component. In such embodiments the motor may be directlymounted to the splitter and the drive shaft will extend through thesplitter into the flow-path.

In order to provide sufficient cooling to the motor when the apparatusis in use the apparatus may further comprise a heat-sink such as a heatconductive casing or heat exchanger that is in direct or indirectthermal connection with the motor and is arranged such that an outersurface of the heat sink is in direct contact with water when theapparatus is in use and submerged. In particular, it is advantageousthat any such heat sink is not completely enclosed within any housing ofthe apparatus but includes a heat exchanger surface that is directly incontact with water when the apparatus is in use and submerged. As willbe readily appreciated any such heat exchanger surface is advantageouslyarranged such that a user will not easily come into contact with theheat exchanger surface when a device comprising the apparatus is in use.

In order to minimise radial flow of water exiting the outlets of thepropulsion passages it is advantageous that radially extending fins arelocated within the propulsion passages. In embodiments of the inventioneach propulsion passage may have one or more, preferably at least four,equally circumferentially spaced radially extending fins.

The apparatus may further comprise a housing substantially containingthe components of the apparatus and wherein the at least one fluid inletis formed at a front end of the housing and the outlets of thepropulsion passages are formed at a rear end of the housing.

A housing of an apparatus of the present invention may be formed in anysuitable manner. If the apparatus forms part of a personal marinepropulsion device the housing may be formed such that it can be used byan individual in a simple manner. For example, the housing may have oneor more handles located on an outer surface to allow a user to hold onto the device when in use. Alternatively or additionally the housing maybe formed as a back-pack and comprise one or more straps to allow a userto wear the device as a back-pack.

The components of the invention may be mounted to a housing in anysuitable manner. In embodiments of the invention one or more of thecomponents may be mounted to the housing by vibration mounts to reducenoise of the apparatus during operation and to reduce wear and tear ofthe components during operation of the apparatus. In embodiments of theinvention the propulsion passages may be mounted to a housing by meansof vibration mounts, this may be particularly advantageous if thepropulsion passages are defined within a splitter formed as a unitarycomponent.

The impeller of the present invention may be formed in any suitablemanner. In embodiments of the invention the impeller may be formed by 3Dprinting using solid laser sintering.

The drive shaft of the apparatus of the present invention may be mountedwithin the apparatus in any manner apparent to the skilled person.Typically, the drive shaft will be mounted within one or more bearings.Such bearings may be of any suitable type including, but not limited to,waterproof bearings or ceramic bearings. Ceramic bearings may bepreferred as waterproof sealing is not required thereby reducing thecost and complexity of the apparatus. The drive shaft may be mountedwithin the apparatus by means of one or more thrust bearings that act totransfer thrust from the drive shaft to the apparatus. Alternatively oradditionally, the drive shaft may be mounted within the apparatus withinone or more brass bushes.

The motor of the apparatus may be a waterproof motor that can beoperated in direct contact with water. This may be preferred as it isnot necessary to mount such motors in waterproof casing and waterproofmotors can be operated in direct contact with water to provide coolingto the water, thereby reducing the need for complex and/or heavy heatsinks.

In order to prevent solid objects entering the fluid flow-pathembodiments of the invention comprise a rigid mesh provided completelyacross the at least one fluid Inlet. A rigid mesh may be formed of anysuitable material. In embodiments of the invention a rigid mesh formedof plastic coated metal is provided. This may be preferred as it canprovide a sufficiently rigid and strong structure whilst also providinggood corrosion resistance. A rigid mesh may have a hexagonal mesh. Ifformed of appropriate material a rigid mesh may be heat-staked to the atleast one fluid inlet in order to avoid gaps or protruding edges aroundedges of the mesh, which could affect flow efficiency through the fluidflow-path.

In order to provide strength to the at least one fluid inlet and/or tohelp direct fluid flow through the fluid flow-path an intake grate maybe provided in the at least one fluid inlet. An intake grate maycomprise one or more support members extending across the at least onefluid inlet and arranged to extend in a direction of fluid flow throughthe at least one fluid inlet. Providing a suitably formed intake gratecan increase laminar flow through the at least one fluid inlet. Anintake grate can extend across a height of the at least one fluid inletto transfer force to the intake grate and thereby prevent damage to theat least one fluid inlet during operation of the apparatus. An intakegrate can be mounted within an at least one fluid inlet in anyappropriate manner including, but not limited to, fastening bolts at ornear a periphery of the intake grate.

Further features and advantages of the present invention will beapparent from the preferred embodiment that is shown in the Figures anddescribed below.

DRAWINGS

FIG. 1 is an image of a device according to an embodiment of the presentinvention;

FIG. 2 is a partial cross-section of components of the embodiment ofFIG. 1;

FIG. 3 is a three-dimensional view of a splitter of the embodiment ofFIG. 1; and

FIG. 4 is a side view of components of the embodiment of the previousFigures.

A personal marine propulsion device 1 substantially consisting of awaterjet propulsion apparatus according to an embodiment of the presentinvention is shown in the Figures. An upper side of the complete device1 is shown in FIG. 1. The housing 2 encloses most of the components ofthe device 1 such that all that is visible in FIG. 1 are outlets 4 ofpropulsion passages 3, a fluid inlet 9, and a top part 26 of the fluidinlet 9. Internal components of the device are illustrated in the otherFigures and described further below. The housing 2 is formed of plasticand is moulded to substantially enclose the internal components. Thedevice 1 is formed as a backpack and comprises shoulder straps (notshown) attached to a lower side of the housing 2 to allow the device tobe worn by a user. A battery pack (not shown) is mounted within thehousing to power a motor 7.

A partial cross-section through components of the device 1 of FIG. 1 isshown in FIG. 2. In particular, this Figure illustrates the relativepositioning of an impeller 6, a motor 7, a drive shaft 8, the propulsionpassages 3, and the fluid inlet 9. A pre-mesh part 9.1 of the fluidinlet and a post-mesh part of the fluid inlet are shown. A flow path 10of fluid passing through the device 1 when it is in use is also shown.

An intake mesh 21 is position in the fluid inlet 9 and acts to preventsolid objects entering the flow path 10. The intake mesh 21 is ahexagonal mesh formed of epoxy coated metal that is heat staked to thefluid inlet 9 for strength and to minimise any gaps or protruding edgesthat could affect flow efficiency through the flow path 10. The intakemesh extends completely across the fluid inlet 9.

An intake grate 22 is also provided within the fluid inlet. The intakegrate 22 comprises three vertically oriented plates that extend alongthe flow path 10 from a rear side of the intake mesh 21. The intakegrate 22 is formed of a thin corrosion resistant material and each plateis bolted within the fluid inlet 9 at a bottom end and are fixed inposition at an upper end by means of a fastening bolt 27 that extendsthrough each plate. The intake grate 22 provides support to the top part26 of the fluid inlet by transferring vertical force away from said toppart 26. The intake grate 22 also acts to improve laminar flow throughthe flow path 10, thereby increasing the efficiency of the apparatus.

The flow path 10 through the device is defined by the fluid inlet 9, theimpeller 6 and a splitter 11, which itself defines the propulsionpassages 3. Details of the splitter 11 are best seen in FIG. 3. Both thefluid inlet 9 and the splitter 11 are unitary moulded components and thefluid inlet 9 and the splitter 11 are connected together around theimpeller 6. The splitter 11 and the fluid inlet 9 may be 3D printedcomponents. The unitary moulding of the splitter 11 allows a bearingseat 24 to be formed in which ceramic bearings 13.1, 13.2 of the driveshaft 8 are slotting into position. A radial groove in the splitter 11also allows a securing ring 23 to be positioned around an outer end ofthe drive shaft 8.

The impeller 6 is located directly in front of the motor 7 and is drivenby the motor 7 by means of the drive shaft 8, which extends from themotor, to the impeller. The impeller 6 is connected to the drive shaft 8by means of a shaft fastener 19. The drive shaft 8 is mounted in thesplitter 11 by means of two ceramic bearings 13.1, 13.2 that allow thedrive shaft to freely rotate. In particular, the drive shaft 8 ismounted within a radial bearing 13.1 and an angular bearing 13.2.Ceramic bearings are used as they do not require watertight sealing. Themotor 7 is fixed to the splitter 11 at a front end of the motor. Themotor 7 is located between the propulsion passages 3 of the splitter 11.

The motor 7 is a waterproof motor that is used in direct contact withwater when the apparatus 1 is in use. Contact with water acts to coolthe motor 7 such that no heat sink or other cooling means is required.

The propulsion passages 3 of the splitter 11 are positioned either sideof the motor 7 and each extend from a propulsion input immediatelybehind the impeller 6 to an output 4 at a rear end of the device 1. Thepropulsion passages 3 are substantially symmetrically positioned withinthe splitter 11 and are mirror images of one another. The propulsionpassages 3 are substantially circular in cross-section and graduallyreduce in diameter from their propulsion input to their output 4. Thisreduction in diameter helps increase and direct thrust generated by thedevice 1. Each propulsion passage 3 has sixradially extending fins 14located therein in order to reduce the radial flow of water exiting thepassages and to thereby preserve the thrust generated by the impeller 6.As the device 1 is intended for use as a backpack the device 1 does notinclude steering means. Instead the device 1 can be steered by the userorienting their body appropriately.

Further details of the device 1 can be seen in FIG. 4. In particularFIG. 4 shows the relative position of the splitter 11, the motor 7, themesh 21, and an intake grate 22. As can be clearly seen, the motor 7 ispositioned between the propulsion passages 3 of the splitter 11. Themotor 7 is positioned and the housing 2 are formed such that an outersurface of the motor 7 is in direct contact with water when the device 1is in use and submerged and thereby provide cooling to the motor. Themotor 7 is fixed to a motor mount 20 at a front end. The motor mount 20is in turn fixed to the splitter 11 to thereby hold the motor 20 in anappropriate position. The motor 20 is connected to the drive shaft 8 bymeans of a shaft coupler 15. A shoulder 25 is provided on the driveshaft 8 adjacent the shaft coupler 15 to locate the drive shaft 8 inposition within the angular bearing 13.2.

The splitter 11 is connected to the housing 2 by means of four jointprofiles 17 provided on each lateral side of the splitter 11. The jointprofiles 17 have eyelets 18 through which the splitter 11 can be mountedto the housing 2 by vibration mounts (not shown) that act to reducenoise and to reduce wear and tear.

When in use the impeller 6 is driven by the motor 7 to rotate via thedrive shaft 8. The motion of the impeller 6 creates a reaction forcefrom water, which is transferred axially into the drive shaft 8 via theshaft fastener 19. The shaft shoulder 25 transfers the thrust into theangular bearing 13.2. The thrust transferred into the angular bearing13.2, from there the reaction force is transferred via the bearing seat24 into the splitter 11 and then into the housing 2 via the jointprofiles 17.

In use the device 1 is strapped to a user's back and when the user issubmerged in water it is turned on. The impeller 6 is then driven by themotor 7 via the drive shaft 8 to draw water through the flow-path 10. Inparticular, water is drawn in the fluid inlet 9, through the impeller 6and out of the device via the propulsion passages 3. This provides awaterjet propulsion system that acts to propel the user forward. Bycontrolling the Speedof the motor 7 the propulsion provided can becontrolled appropriately. The user can then steer themselves by movingtheir body appropriately. In order that a user can control the speed ofthe motor and can turn the motor on and off control means (not shown)are provided as a handheld controller.

1. A waterjet propulsion apparatus for a propulsion device comprising amotor, an impeller driven by the motor via a drive shaft, and a powersource; wherein: a fluid flow-path is formed through and containedwithin the apparatus, the flow-path extending from at least one fluidinlet located at a front end of the apparatus through two propulsionpassages, each propulsion passage extending from a propulsion inlet toan outlet located at a rear end of the apparatus; the impeller islocated within the flow-path, after the at least one fluid inlet, andbefore the propulsion inlet of the each of the propulsion passages; andthe motor is located outside of the flow-path, within a rear portion ofthe apparatus, between the two propulsion passages, and behind theimpeller.
 2. An apparatus according to claim 1, wherein each propulsionpassage reduces in cross-section from its propulsion inlet to itsoutlet.
 3. An apparatus according to claim 1, wherein the outlets of thepropulsion passages are substantially cylindrical or rectangular.
 4. Anapparatus according to claim 1, wherein the propulsion passages aredefined within a splitter formed as a unitary component.
 5. An apparatusaccording to claim 4, wherein the motor is mounted to the splitter andthe drive shaft extends through the splitter into the flow-path.
 6. Anapparatus according to claim 1, further comprising a heat-sink that isin thermal connection with motor and is arranged such that the heat sinkis in direct contact with water when the device is in use.
 7. Anapparatus according to claim 1, wherein radially extending fins arelocated within the propulsion passages to direct water expelled from thedevice.
 8. An apparatus according to claim 1, wherein the at least onefluid inlet is formed at a front end of the housing and the outlets ofthe propulsion passages are formed at a rear end of the housing.
 9. Anapparatus according to claim 8, wherein the housing has one or morehandles located on an outer surface to allow a user to hold on to thedevice when in use.
 10. An apparatus according to claim 8, wherein thehousing is formed as a back-pack and comprises one or more straps toallow a user to wear the device.
 11. An apparatus according to claim 8,wherein one or more components of the apparatus are mounted to thehousing by means of vibration mounts.
 12. An apparatus according toclaim 1, wherein the impeller is formed by solid laser sintering.
 13. Anapparatus according to claim 1, wherein the drive shaft is mountedwithin the apparatus on ceramic bearings.
 14. An apparatus according toclaim 1, wherein the drive shaft is mounted within the apparatus bymeans of at least one thrust bearing.
 15. An apparatus according toclaim 1, wherein the motor is water-proof and can be operated when indirect contact with water.
 16. An apparatus according to claim 1,wherein a rigid mesh is provided across the at least one fluid inlet toprevent solid objects entering the fluid flow-path.
 17. An apparatusaccording to claim 16, wherein the mesh is heat-staked to the fluidinlet.
 18. An apparatus according to claim 15, wherein the mesh isformed of epoxy coated metal.
 19. An apparatus according to claim 1,wherein a grating is provided in the at least one fluid inlet.
 20. Anapparatus according to claim 1, wherein the apparatus is engaged with apersonal marine propulsion device.